The development of digital printing technology, such as thermal inkjet printing, has made the use of computer printers less expensive and thus, widely available to all computer users. Currently available printers are able to produce full-color and highly detailed images. The widespread use of digital printing technology in residential and commercial environments has created challenges with respect to traditional printing media on which the images are formed, particularly when pigmented ink is utilized. Current print media, when used in combination with pigment inks, often suffer from poor black and color optical density, ink bleeding and smearing, extended dry times, and image strike through.
In order to overcome these problems, divalent metal salts, e.g., calcium chloride, have recently been added, as an ink fixative, to surface sizing processing of the print media to achieve improved media properties. However, to achieve such effects, the calcium chloride needs to be used in a large concentration, e.g., from 6 to 12 kg salt per ton (T) of paper. Such a high loading of chloride-containing compounds promotes drastic corrosion of the paper milling equipment used to produce the print media, and significantly reduces the life span of the salt-contacting parts of the paper manufacturing equipment, including, for example, sizing rolls.
Another drawback commonly associated with the use of calcium chloride salt arises from its exothermic dissolution in water. A significant amount of heat is produced when large batches of calcium chloride salt solution are prepared, as is customary in commercial paper manufacturing processes. Solution temperatures can easily reach over 90° C. or more. The chloride-containing vapors from such a heated solution can cause serious health and safety issues to workers involved with the mixing process.
Further, calcium chloride is very moisture-absorbent. The use of this type of salt can easily change the stiffness of the paper due to absorption of water into the paper. This inevitably causes some issues related to the runnability of the media in the print. These issues can cause, for example, paper jamming and/or multi-picking of the sheets from a paper tray.
In view of the foregoing, there is a need in the art for a paper or print medium having improved print quality and print properties when printed using pigment ink.